1. Field of the Invention
The present invention relates to a pneumatic tire, more particularly to a bead structure being capable of reducing the weight of the bead portions without deteriorating the bead durability.
2. Description of Related Art
In pneumatic tires used under relatively heavy loads such as heavy duty tires for trucks and buses, light truck tires and the like, a large volume of bead apex rubber is disposed between a carcass ply turnup portion and main portion to increase the bead rigidity and thereby to decrease deformation of the tire under heavy loads.
Recently, in order to decrease tire weight, the bead structures have been reexamined, and many efforts have been made to decrease the weight of the bead portions by decreasing the volume of bead apex rubber.
In such tires of which the bead apex rubber is very small, movements and bending deformation of the carcass plies under loads are relatively large. Therefore, as the tension of the carcass cords is large and a large stress concentrates on contacting points with the bead core, the carcass cords are liable to be cut.
It is therefore, an object of the present invention to provide a pneumatic tire, in which the carcass cords are prevented from being cut and the durability of the bead portions are improved.
According to one aspect of the present invention, a pneumatic tire comprises
a tread portion,
a pair of sidewall portions,
a pair of bead portions with a bead core therein,
a carcass ply extending between the bead portions and turned up around the bead core in each bead portion to form two turnup portion and a main portion therebetween,
each said turnup portion extending radially outwardly so as to adjoin the main portion from a certain height above the bead core, and
a bead core cover disposed between the carcass ply and the bead core for preventing cords of the carcass from directly contacting the bead core, the bead core cover being made of a textile fabric and/or a rubber layer.
Preferably, the bead core cover is made of a textile fabric of organic fiber yarn such as nylon, rayon, polyester and the like.